Method for cleaning metal surfaces

ABSTRACT

IN ACCORDANCE WITH CERTAIN OF ITS ASPECTS, THIS INVENTION RELATES TO A PROCESS FOR CLEANING PRETREATED METAL SURFACES BEARING INORGANIC AND ORGANIC CONTAMINANT CONSISTING ESSENTIALLY OF THE STEPS OF IMMERSING SAID PRETREATED METAL SURFACE IN WATER AND THEN IMMERSING SAID PRETREATED METAL SURFACE IN WATER-IMMISCIBLE ORGANIC SOLVENT TO FORM A NON-STABLE SUSPENSION OF WATER IN ORGANIC SOLVENT THEREBY OBTAINING A BRIGHT, CLEAN METAL SURFACE FREE OF CONTAMINANT, AND COATING SAID BRIGHT, CLEAN METAL SURFACE.

United States Patent 3,560,352 METHOD FOR CLEANING METAL SURFACES Johannes van Garderen, Baarn, and George G. Busch, Bussum, Netherlands, assignors to M&T Chemicals Inc., New York, N. N0 Drawing. Filed Sept. 23, 1965, Ser. No. 489,745 Int. Cl. C23b 1/00; B08b 7/00; B44d 1/34 US. Cl. 204-32 3 Claims ABSTRACT OF THE DISCLOSURE In accordance with certain of its aspects, this invention relates to a process for cleaning pretreated metal surfaces bearing inorganic and organic contaminant consisting essentially of the steps of immersing said pretreated metal surface in water and then immersing said pretreated metal surface in water-immiscible organic solvent to form a non-stable suspension of water in organic solvent thereby obtaining a bright, clean metal surface free of contaminant, and coating said bright, clean metal surface.

Metal surfaces which are to be treated, such as by coating as with a metal layer (by electrolytic or other means) or with a coating chemically attached to the metal surface (such as a phosphate or a chromate coating) or with an organic coating (such as lacquer or paint), should first be cleaned of materials which may interfere with the coating treatment.

These interfering materials or contaminants may be of an organic or inorganic nature and may be left on the metal surface after a pretreatment, e.g., bufiing, polishing, forming, etc., or because an anti-corrosion material had been applied to the metal surface.

In the prior art, cleaning methods usually have attempted to remove organic material such as mineral oils and greases, vegetable oils and greases and animal oils and greases. These impurities have been removed by immersion of the metal surface in a solvent, or by treatment in a solvent in the vapor phase, or by treatment by means of immersion in or spraying with an emulsion of a solvent in water.

These methods had the disadvantage that they left as contaminant on the metal surfacea layer of inorganic particles which still has to be removed as by wiping In practice this has been done by mechanical means during cleaning, e.g. by treating the metal surface with a solvent in which plastic balls have been agitated or by ultrasonic vibration of the cleaning solvent or of an alkaline solution.

According to another method an attempt was made to chemically remove all contaminants by treating a metal surface with non-stable emulsions of solvent in water. This method, however, has the following disadvantages:

(1) Owing to the strong agitation which is always necessary when treating metal surfaces, in the long run stable emulsions are formed, a phenomenon caused by the drag-in of organic material. This will hamper the removal of the inorganic particles.

(2) In view of the toxicity or the flash point of the organic solvents unlimited increase of temperature, which would be necessary for the removal of greases with a high melting point or burnt-in greases and oils, is not possible.

It is an object of this invention to provide a non-stable suspension of organic solvent in water which may be used in a method for cleaning metal surfaces whereby substantially all contaminants which may interfere with subsequent treatments of the metal surface are removed. Other objects will be apparent on the inspection of the following description.

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This invention according to certain of its aspects is directed to a process for cleaning pretreated metal surfaces bearing inorganic and organic contaminant by immersing said pretreated metal surface in water and then immersing said pretreated metal surface in organic solvent thereby obtaining a bright, clean metal surface free of contaminant.

In accordance with this invention, the metal surface may, if desired, be rinsed after said immersion in water and prior to said immersion in organic solvent.

When the process of this invention is practiced, nonstable suspension of water in organic solvent may be formed on the metal surface which removes substantially all contaminants including inorganic particles and organic materials such as grease. Thus, further delay in processing is unnecessary as mechanical cleaning steps are not required. This is particularly advantageous when metals are to be treated on a mass production basis. The cleaned metal surface obtained by this invention is a bright, clean surface.

According to certain preferred aspects of this invention, a metal surface, say steel, may be pretreated with buifing compound which may contain tallow, carbon and talcum. The pretreated metal surface may then be immersed in water which may most preferably have dispersed therein 10-50 g./l. of a surface-active agent containing carboxylic groups such as mono-ethanolamine-myristinate, tri-ethanolamine-oleate, mono-ethanolaminestearate, alkali metal laurate, alkali metal palmitate or combinations of the foregoing agents. Most preferably, when surface-active agent is present the water may also contain 10-50 g./l. of a non-ionic dispersing agent such as nonyl-phenol-polyglycol-ether. During immersion the water may be maintained at 50 C.- C., most preferably 70 C.100 C. and at a pH of 6.7l1.5. After the water immersion, the metal surface may optionally be rinsed and then immersed in the organic solvent. Typical organic solvents include benzene, butyl Cellosolve, painters naphtha (i.e. any of a number of narrow-boiling-range fractions of petroleum with boiling points of about 93 149 C. such as varnish makers naphtha, petroleum spirits, petroleum thinner, mineral spirits, turpentine substitute, mineral thinner, mineral turpentine, or white spirits), or combinations of the foregoing solvents.

In accordance with certain of its aspects this invention provides a process for electrodepositing metal comprising bufiing a metal surface; cleaning by immersing the pretreated metal surface in water and then immersing said pretreated metal surface in organic solvent thereby obtaining a bright, clean metal surface; activating said metal surface; and electrodepositing metal on the cleaned activated metal surface whereby the electrodeposit is adhered to said cleaned metal surface.

In order to point up clearly the novel features of this invention and to illustrate the unexpected results obtained through its practice, the following examples may be prepared.

EMMPLE 1 Cold-rolled steel sheets may be pretreated with bufiing compound containing tallow, carbon, and talcum. The pretreated sheets may be immersed in an aqueous solution containing 10 g./l. of mono-ethanolamine-myristinate for 10 minutes at a temperature of 70 C. The sheets may then be dipped into mineral turpentine. The thus obtained sheets may be characterized by their bright, clean surface, which does not require wiping.

The cleaned sheets may subsequently be activated cathodically and then have nickel electrodeposited thereon. The nickel may be free of stains and have good adhesion to the metal surface.

3 EXAMPLE 2 Cold-rolled steel sheets may be pretreated with bufiing compound containing tallow, carbon, and talcum. The pretreated sheets may be immersed in an aqueous solution containing 20 g./l. of potassium laurate for minutes at a temperature of 50 C. The sheets may then be dipped into benzene solvent, which is immiscible with the aqueous solvent. The thus obtained sheets may be characterized by their bright, clean surface, which does not require wiping.

The cleaned sheets may subsequently be anodically activated and then have nickel electrodeposited thereon. The nickel may be free of stains and have good adhesion to the metal surface.

EXAMPLE 3 Cold-rolled steel sheets may be pretreated by polishing with a polishing mop which leaves a surface of abrasive dust containing grease. The pretreated sheets may be immersed in an aqueous solution containing g./l. of mono-ethanolamine-stearate and 20 g./ 1. of nonyl-phenolpolyglycol-ether for 15 minutes at a pH of 8.5 and at a temperature of 85 C. The sheets may then be immersed in a second bath containing a mixture of 80 parts by volume of benzene and 20 parts by volume of butyl Cellosolve. The thus obtained sheets may be characterized as totally free of the abrasive dust and as clean and bright, without requiring wiping.

EXAMPLE 4 As a control, cold-rolled steel sheets may be pretreated with buffing compound containing tallow, carbon and talcum. The pretreated sheets may be degreased with trichloroethylene. The surface thus obtained may be substantially free of organic contaminants including grease, but a greyish white dust of inorganic particles may still be found on the surface of the sheets. The sheets may then be water rinsed, but this also does not remove the dust. The dust may only be removed mechanically, as by wiping.

Although this invention has been illustrated by reference to certain specific examples, many modifications thereof which clearly fall within the scope of the invention will be apparent to those skilled in the art.

What is claimed is:

1. A process for cleaning pretreated metal surfaces bearing inorganic and organic contaminant consisting essentially of the steps of immersing said pretreated metal surface in water, said water having dispersed therein between about 10-50 g./l. of a surface active agent selected from the group consisting of mono-ethanolamine-myristinate, tri-ethanolamine-oleate, mono-ethanolamine-stearate, alkali metal laurate, alkali metal palmitrate, and mixtures thereof, and between about 10-50 g./l. of nonylphenyl-polyglycol ether; maintaining said water at a temperature between about 100 C. and at a pH of between about 6.711.5; then immersing said pretreated metal surface in water-immiscible organic solvent of a mixture of parts by volume benzene and 20 parts by volume butyl Cellosolve to form a non-stable suspension of water in organic solvent thereby obtaining a bright, clean metal surface free of contaminant, and coating said bright, clean metal surface.

2. The process for cleaning pretreated metal surfaces as claimed in claim 1 wherein said organic solvent is mineral turpentine.

3. A process for cleaning pretreated metal surfaces bearing inorganic and organic contaminant for the subsequent electroplating thereof comprising the steps of:

(a) immersing said pretreated metal surface in water having dispersed therein between about 10-50 g./l. of a surface active agent selected from the group consisting of mono-ethanolamine-myristinate, triethanolamine-oleate, mono-ethanolamine-stearate, alkali metal laurate, alkali metal palmitate, and mixtures thereof, and between about 1050 g./l. of nonyl-phenyl-polyglycol ether;

(b) immersing said-pretreated metal surface from (a) in an organic solvent selected from the group consisting of benzene and painters naphtha having a boiling range of about 93 149 C. to form a nonstable suspension of water in organic solvents, thereby obtaining a bright, clean metal surface free of contaminant; and

(c) electroplating said bright, clean metal surface.

References Cited UNITED STATES PATENTS 2,383,434 8/1945 Houis 13441 2,744,555 '5/1956 Nicholson et al. 1486.l5 2,899,367 8/1959 Veeder 20432 3,021,235 2/1962 Schumacher 13440X 3,081,203 3/1963 Beuscher 134-28 3,113,035 12/1963 MacCormack ll7-50 3,189,532 6/1965 Chow et al. 20428 3,317,411 5/1967 Letendre 204-29 FOREIGN PATENTS 685,734 1/1953 Great Britain 204-32 OTHER REFERENCES Lesser article, Soap and Sanitary Chemicals, October 1952, pp. 42-45 and 169.

TA-HSUNG TUNG, Primary Examiner T. TUFARIELLO, Assistant Examiner 

